1. Field of the Invention
The present invention relates to a pretreatment system for analyzing impurities contained in a flat sample, and more particularly, to a pretreatment system for analyzing impurities contained in a flat sample where a pretreatment solution is applied on, for example, the surface of a wafer for semiconductor manufacturing, or a glass for a liquid crystal display, to dissolve impurities and thereby to easily analyze and estimate metal contamination and ion contamination.
2. Description of the Related Art
Generally, in semiconductor manufacturing processes, detecting wafer contamination is crucial to increase productivity and to control contamination levels. Although particle contamination can be identified by a high intensity light or an electronic microscope, metal contamination or ion contamination formed on the surface of a wafer can by identified by a pretreatment process.
In the conventional pretreatment process, as shown in FIG. 1, a pretreatment solution such as distilled water, HF, H.sub.2 O.sub.2, or HNO.sub.3, etc. is first dropped onto the surface of a sample 10, such as a flat wafer or a glass for a liquid crystal display, and then the surface is scanned in the direction of an arrow as shown in FIG. 1. Then, the pretreatment solution having impurities absorbed and dissolved therein is collected, and the contamination level is analyzed by an atomic absorption spectrometer or a high performance ion chromatography.
The pretreatment process of the prior art can analyze contamination levels to some extent in certain situations, such as when the sample is a wafer made from pure silicon and the wafer has not passed through an integrated circuit forming process. However, when a integrated circuit, etc. is formed on the wafer, or a layer such as polycrystalline silicon, Si.sub.3 N.sub.4, etc. is deposited onto the surface of the wafer, it is very difficult not only to scan the surface of the sample, but also to determine the proper amount of the pretreatment solution to be supplied to the sample. This is because the amount of pretreatment solution varies with changes in surface conditions, such as hydrophilic properties. Accordingly, the amount of the collected pretreatment solution is changed each time, thereby making it difficult to implement quantitative analysis. Furthermore, when the pretreatment solution is held for a long time to sufficiently dissolve the impurities in the pretreatment solution, the pretreatment solution is apt to become contaminated due to surrounding environmental conditions.